TOWARDS A HOLISTIC RATE ADAPTION FOR 802.1 1N/AC MIMO SYSTEMS

Master'sMASTER OF SCIENC

Simulation of three dimensional current spreading in photonic crystal VCSEL structures

An efficient simulation technique for calculating the current distribution in a Vertical Cavity Surface Emitting Laser (VCSEL) is proposed and implemented. The technique consists of a hybrid 1D/3D approach to the problem. The 3D aspect of simulation is essential for devices like a photonic crystal VCSEL where the existing 2D simulation techniques are inadequate. The modular approach of the technique is advantageous, as it provides exibility in dealing with device simulations of varying complexity. It also provides a relatively short simulation time, beneficial for exploring a large design parameter space. The box integration technique is used for discretizing the equations and sparse matrix methods are used in solving the matrices. Simulation results and comparisons are provided for various aspects and modules of the simulator. The results for a few sample simulations indicate that the analysis has reasonable agreement with experimental results. The simulation error can be reduced using more accurate models for the active region of the laser.M.S.Committee Chair: Klein, Benjamin; Committee Member: Citrin, David; Committee Member: Ferguson, Ia

Machine learning-based recognition on Crowdsourced Food Images

With nearly a third of the world’s population suffering from food-induced chronic diseases such as obesity, the role of food in community health is required now more than ever. While current research underscores food proximity and density, there is a dearth in regard to its nutrition and quality. However, recent research in geospatial data collection and analysis as well as intelligent deep learning will help us study this further. Employing the efficiency and interconnection of computer vision and geospatial technology, we want to study whether healthy food in the community is attainable. Specifically, with the help of deep learning in the field of health geography, we aim to utilize image recognition to gather and model the role of the community food environment in shaping obesity and related chronic diseases

Non-Equispaced Fast Fourier Transforms in Turbulence Simulation

Fourier pseudo-spectral method on equispaced grid is one of the approaches in turbulence simulation, to compute derivative of discrete data, using fast Fourier Transform (FFT) and gives low dispersion and dissipation errors. In many turbulent flows the dynamically important scales of motion are concentrated in certain regions which requires a coarser grid for higher accuracy. A coarser grid in other regions minimizes the memory requirement. This requires the use of Non-equispaced Fast Fourier Transform (NFFT) to compute the Fourier transform, by solving a system of linear equations. To achieve similar accuracy, the NFFT needs to return more Fourier coefficients than the number of non-equispaced gridpoints, making it an under-determined system. The minimum L2 norm solution of the system is refined using an iterative reconstruction algorithm, FOCUSS. The NFFT and FOCUSS algorithms yield accurate results with smaller test case of a Direct Numerical Simulation on a grid of 64 gridpoints in each dimension, using Taylor green initial condition. The computational speed for this case was found to be unacceptably slow and few methods to improve the performance have been discussed. The approach of NFFT and FOCUSS was tested on a line extracted from 3-dimensional turbulent flow field. Fourier transform of the extracted line, sampled on 1024 non-equispaced gridpoints, computed for 2048 coefficients and the corresponding numerical derivative are found to be inaccurate. It can be observed that the NFFT and FOCUSS approach works for sparse Fourier transform, but not for turbulent fields having a wideband Fourier transform

Human Mobility Patterns Linked to COVID-19 Prone Locations

Since the onset of COVID-19 in late 2019, the virus has affected human mobility and the economy in many ways. Countries closed their borders to non-essential travelers, some cities had to quarantine, and many businesses had to shut down and pivot to online customer interactions (the feasibility was largely dependent on a business’s sector: the hospitality industry versus the technology industry). These all contributed to unprecedented numbers of people losing their jobs and sharp contractions in economies worldwide––on top of 2.69 million people who have died of COVID-19 as of March 19th, 2021. During this time, researchers have focused their attention on assisting the broader community by releasing findings and developing projects to expand our knowledge on various aspects of the COVID-19 pandemic. In light of beginning economic recovery, an important question for researchers is how to identify when it is safe to reopen businesses and other places of gathering

Rising incidence of hip fractures in Sindhudurg west coast of Maharashtra, South India (2000 to 2011)

Background: The incidence of hip fractures in Sindhudurg, west coast of Maharashtra has been reported in relation to age and gender.Methods: Using the medical records and X-ray registers from May 2000 to October 2011, all patients of proximal femoral fractures were recorded and included in this study. The data was cross checked doubly with details of indoor case papers against ward admission and operation theatre registers, were found to be congruent after verifying the names of patients.Results: The total male incidence was bimodal with moderate peaks at 31 to 50 years and very high at 51 to 70 years. The female incidence with peaks at 41 to 60 years with regular steady increase up to 80 years. Males of 31 to 70 years 2.5 times more likely to sustain a fracture (95% CI 2.3 to 2.8) than females. Females between 40 to 60 years 2.8 times more likely to sustain fracture than males (95% CI 2.5 to 3.0). The trend was stable from year to year. This high increase in hip fractures in men of 51 to 70 years incidence documented osteoporotic fractures in contrast with too much emphasis on the importance of menopause in hip fractures.Conclusions: Despite wide variations in age specific hip fracture rates over a decade, reasons for differences are not clear. From 2000 to 2011, the hip fractures in district hospital increased by a factor of 6.6%, 14.34% in both the genders above the age of 41 years in parallel with hospital admissions.

Adoption and Utilization of Drones for Advanced Precision Farming: A Review

India is the considerable maker of agricultural products but has very low agricultural productivity. Productivity of farm needs to be improved in a way that farmers can earn more profit from the same piece of land with less labor. Advanced precision farming may able to do it. Advanced precision farming technologies include use of drones, unmanned aerial vehicles (UAV's), Airborne Digital Photography (ADP) etc. UAV’s are controlled remotely by telemetry, where the operator keeps up visual contact with the aircraft using GPS and inertial guidance. The initial uses in agriculture have been for remote sensing, with a prominence on the visual investigation of crop yield or farm field conditions and for tracking resources like machinery, workers or product. This paper presents a review on utilization of precision farming using aerial based system such as drones or UAV’s for sustainability farming

Businesses in high-income zip codes often saw sharper visit reductions during the COVID-19 pandemic

As the COVID-19 pandemic unfolded, the mobility patterns of people worldwide changed drastically. While travel time, costs, and trip convenience have always influenced mobility, the risk of infection and policy actions such as lockdowns and stay-at-home orders emerged as new factors to consider in the location-visitation calculus. We use SafeGraph mobility data from Minnesota, USA, to demonstrate that businesses (especially those requiring extended indoor visits) located in affluent zip codes witnessed sharper reductions in visits (relative to pre-pandemic times) outside of the lockdown periods than their poorer counterparts. To the extent visits translate into sales, we contend that post-pandemic recovery efforts should prioritize relief funding, keeping the losses relating to diminished visits in mind.Comment: 18 pages, 6 figures, 3 table